Soft, poured substrates of gypsum-based materials, which may be over gypsum boards or other boards, or of wood fiber-filled, inorganic, hydraulic cement are used widely in roofing installations. Materials for such substrates of gypsum-based materials, over gypsum boards or other boards, are available commercially from various sources. Materials for such substrates of wood fiber-filled, inorganic, hydraulic cement are available commercially from Tectum, Inc., of Newark, Ohio, under its TECTUM.TM. trademark.
In fastening blankets of roofing insulation, such as rigid slabs of fibrous insulation or of foamed insulation, to such substrates, possibly with other roofing materials therebetween, fastening assemblies of a type disclosed in Blucher et al. U.S. Pat. No. 4,642,012 and 4,856,951 are used widely. Such fastening assemblies are available commercially from ITW Buildex (a division of Illinois Tool Works Inc.) of Itasca, Ill., under its GYPTEC.TM. trademark.
Typically, as disclosed in each of the aforesaid patents, such a fastening assembly utilizes four separate pieces, namely an elongate screw having threads at one end of its shank and having a head, an anchoring element attached to the threaded end of the screw shank, a washer between the screw head and the anchoring element, and a plate. The plate may be also called a roofing washer. The threaded end of the shank of the screw is threaded into an axial bore of the anchoring element. The anchoring element has external threads designed to be highly resistant to pull-out in a soft substrate. The plate is disposed between the washer and a rigid slab of roofing insulation when the screw is driven so as to drive the anchoring element.
Giannuzzi U.S. Pat. Nos. 4,763,456 and 4,892,429 contain similar disclosures of a fastening assembly employing a screw having a generally uniform crest diameter and a progressively tapered root diameter, along with a roofing washer. Bidwell U.S. Pat. No. 74,489 discloses a similar screw having a generally uniform crest diameter and a progressively tapered root diameter.
The aforenoted application (Ser. No. 07/604,459 filed Oct. 29, 1990) discloses a composite fastener in an improved form. As disclosed therein, the composite fastener comprises a roofing screw in an improved form and a roofing washer in an improved form. The roofing screw disclosed therein has two locking tabs, which are used to lock such screw to the roofing washer disclosed therein. Each locking tab has a distal edge, which is bevelled in such manner that one end of the distal edge is closer to the screw tip, as compared to the other end of the distal edge, and that the closer end leads the other end when the screw is driven. The locking tabs flex as the screw is driven through the washer.
This invention provides further improvements in the composite fastener disclosed in the aforenoted application and in the roofing screw disclosed therein.